1. Field of the Disclosure
The present disclosure relates to electronic devices, in general, and more particularly to a method and apparatus for sensing fingerprints.
2. Description of the Related Art
At present, an electronic device such as a smart phone or a tablet Personal Computer (PC) has been popularized, and the use of the smart phone which utilizes a fingerprint sensor is more and more increased in recent years. The fingerprint sensor used in the smart phone is used more frequently than before due to easy usage and high security.
However, with an increase in usability and popularity of the fingerprint, people tend to store or confirm personal information through fingerprint authentication, and if the fingerprint is not supported, its damage may be significant. Since the fingerprint has relatively high security, a dependency of users is increased, and thus an effort for hacking this is also increased. Therefore, a fingerprint recognition technique having a higher level of security is necessary.
However, the fingerprint sensor must improve security in a state of not damaging usability. In most cases, the fingerprint sensor performs a confirmation in general by normalizing and imaging a portion in which a difference between a ridge and valley of a finger is generated in a process of emitting and receiving light, electrodes, sound, or the like.
Conventionally, user authentication is achieved through an algorithm which recognizes only a shape of the fingerprint by the use of a difference of reflection coefficients of the ridge and the valley in the fingerprint sensor or a difference of electrical signal strength.
However, in this method, when a fingerprint is created with other materials by copying a fingerprint of a user and thereafter is coated with a material having a permittivity similar to a human tissue, a fake fingerprint cannot be distinguished from that of a real user, which results in being vulnerable to security. For example, a sound wave impedance of human skin is 1.63, and a sound wave impedance of a material such rubber is 1.3 which may be similar to the sound wave impedance of a human skin tissue.